So your looking not for a new vid board but for a card that will just do tv out? I've seen plenty of cards that will do TV in for capturing and such, but not sure about one that will just copy whats on the screen and do a tv out...since usually it is built onto the vid boards..you might want to just do a google search and check companies like dazzle which specialize in video in/out products.
the simplest way would probably be to get a vga to rca or svideo converter. they're fairly cheap, less or the same as another video card. it basically connects between the video card vga output and the monitor. it converts the signal to fit on tv. some support quite a high resolutoin i believe, up to 1600x1200x32bit last i saw. hope that helps